1. Field of the Invention
The present invention relates to a video distribution technique for distributing a video image via a network.
2. Description of the Related Art
Recently, a video distribution system for distributing live video images over a network, such as the Internet, has been emerging on the scene. In such a system, it is desirable that a viewer apparatus can perform camera control operations, such as panning, tilting, zooming, and backlight correction, on a camera server.
Panning, tilting, and zooming operations (these three operations are also sometimes collectively referred to as “PTZ” using their first letters) are performed by a conventional mechanical method (mechanical PTZ) or an electronic method (electronic PTZ) based on image processing. In the mechanical PTZ, a panning, tilting, or zooming operation is performed by driving an optical system of lenses and the like, and a panhead mechanism, by motor(s). On the other hand, in the electronic PTZ, a partial image is cut out from a picked-up wide-range image, and then the cut-out image is subjected to image processing, whereby a desired panned, tilted, or zoomed image is obtained (see Japanese Laid-Open Patent Publication Nos. H09-289607 and H09-261522).
The electronic PTZ is advantageous in that the panhead mechanism indispensable to the mechanical PTZ can be dispensed with. However, in general, the electronic PTZ cannot provide a video image (intermediate video image) picked up during the panning, tilting, or zooming operation, which the mechanical PTZ can provide. To solve this problem, there has been proposed a related technique called the mechanical PTZ emulation. The related technique makes it possible to form an intermediate video image from images immediately before and after application of the panning, tilting, or zooming operation, by interpolation, and distribute the intermediate video image.
However, in the conventional video distribution system, it is impossible to perform flexible switching between an electronic PTZ distribution mode and a mechanical PTZ emulation distribution mode. The other problems with the prior art will become apparent from the overall description of the present specification.